Thermoplastic resins can exhibit excellent physical properties such as low specific gravity, good moldability and good impact resistance, as compared with glass or metal. With the trend of low cost, larger and light weight electric and electronic products, plastic products made of thermoplastic resins are quickly replacing existing glass or metal-based products, thereby broadening applications thereof from electric and electronic products to automobile components. In line with this trend, functions as exterior materials and external appearance are increasingly important. In addition, there is a strong need for resins having good scratch resistance for ensuring stability from exterior shock or scratch or flame retardancy for ensuring stability against fire.
Polycarbonate resins among thermoplastic resins exhibit not only excellent mechanical strength, flame retardancy, transparency and weather resistance, but also good impact resistance, thermal stability, self extinguishability, dimensional stability and the like, and thus have been widely applied to electric and electronic products and automobile components. In addition, polycarbonate resins can replace glass in products such as lenses where both transparency and impact resistance are required. However, polycarbonate resins have a disadvantage in that they exhibit very poor scratch resistance.
Meanwhile, acrylic resins, specifically polymethyl methacrylate (PMMA) resins, have excellent transparency, weather resistance, mechanical strength, surface gloss, adhesion, and the like, in particular, remarkably excellent scratch resistance. However, acrylic resins have drawbacks in that impact resistance and flame retardancy are very poor.
In order to overcome these problems, one method is to prepare a polycarbonate (PC)/PMMA resin by mixing polycarbonate (PC) and acrylic resins, for example polymethyl methacrylate (PMMA). In PC/PMMA mixed resins, a (meth)acrylic copolymer having a high index of refraction is employed to prepare an alloy resin of polycarbonate and (meth)acrylic resins having high flame retardancy and scratch resistance, thereby improving compatibility. However, due to a low content of flame retardant in the alloy resin of polycarbonate and (meth)acrylic resin, the alloy resin can exhibit almost no flame retardancy and is likely to suffer from deterioration in mechanical properties when containing a flame retardant. Furthermore, when preparing a resin by adding a phosphorus monomer flame retardant, the monomer can escape from the resin, which can cause environmental contamination.